Electric switch construction



July 7, 1942.y M, W, EATON 2,289,108

' ELECTRIC SWITCH CONSTRUCTION Filed NOV. 15, 1940 z2 @I Z 3 l 6v Patented July 7, 1942 2,289,108 ELECTRIC SWITCH CONSTRUCTION Malcolm W. Eaton, Freeport, 11h, 'assigner to Micro Switch Corporation, Freeport, lll., a corporation of Illinois Application November l5, 19M), Serial No. 365,780 Claims. (Cl. ld-470) 'I'he present invention is related to electric switches.

Objects of this invention include the provision of a rugged, compact, low cost electric switch construction, suitable for use as a limit switch or the like, the provision of such a switch that operates in response to a small motion of its actuating member while permitting a relatively large overtravel of the actuating member beyond the switch operating point thereof, the provision of such a switch requiring a small operating elort and having inherent accuracy and reliability of operation, the provision of an improved switch actuating mechanism, and the provision of an improved electric switch construction. Other objects of the invention will become apparent from the following description of a specic embodiment thereof which serves by way of example to illustrate the manner in which the invention may be carried out, without thereby limiting'the invention to the specific details of the example. In the drawing:

Fig. l is an elevational View showing the interior of the switch of my invention;

Fig. 2 is a partial sectional view taken along the line 2 2 of Fig. 1;

Fig. 3 is a partial sectional view taken along the line 3-3 of Fig. 2, showing the mechanism of Fig. 1 in a diierent operatedposition, and,

Fig, 4 is a partial sectional view taken along the line i-d of Fig. 3.

In the drawing, a shallow die cast metal housing l2 is closed by a'gasketed cover lil (Figs. 2 and 4) held by screws in the tapped holes it. Within the housing, a unitary elongated rectangular switch it, nts accurately onto a pair of supporting ping` 20 (Figs. 1 and 2), lies horizontally as seen in Fig. l across the housing, and fills the central portion thereof so as to divide the space within the housing into two substantially separated spaces above and below the unitary switch i8.

This switch I8 may be of the type described and claimed in Patent 1,960,020 to P. K. McGall.

Switch I8 has a small operating pin 22 that projects vertically from its top and is adapted to be depressed for operating the electric contacts within the switch i8. It also has terminals 2t on its bottom face (Fig. 2). Accordingly the actuating pin 22 and the terminals 2d are located in the spaces respectively above and below thev unitary switch i8. An aperture in the side of the housing is tted with a conduit bushing 26 and opens into the lower or terminal space. This lower space in the housing permits conductreciprocable thereon ing wires to be brought in easily for attachment to the terminals 2d of the switch. The unitary switch I8 itself may be lifted off its supporting pins 20 while the circuit wires are.being tted to it and then slipped back into place.

The space in the housing above the unitary switch I8 contains a mechanism for actuating the switch. This mechanism includes a reciprocal plunger 20 extending through the wall of the housing and supported thereby. The plunger 2t has its supporting bearings partly in an enlargement or boss it in the wall of the housing and partly in an internal bracket 30 spaced slightly from the boss 2t. A felt washer 32 held by a metal washer ii and a spring Se, bearing against the bracket 30 provides a seal against oil and moisture. The right end 2l of the plunger, that extends inside the housing, has a smaller diameter than the part that lits the supporting bearings. A rider i0 consists of a metal strip di having Atwo downturned ends t2 and d@ perforated to iit the large and small diameters respectively of the plunger Z, so as to be (Figs. l and 3). A C-shaped key it clamped in a circumferential groove near the inner end of the large diameter portion oi the plunger 26 serves as a stop for preventing the rider Q0 from sliding forward (to the right as seen in Figs. 1 and 3) oi the end of the plunger. A spring it encircling the small diameter portion 2l of the plunger bears at one end against the shoulder between the large and small diameters of the plunger, and at its forward end against the forward end dit of the rider 30. Accordingly, the spring t@ urges the rider l0 forward on the plunger until it stops against the key 5%.

A bell crank 50 is pivoted on a pin-52' imme diately below the plunger 2S and spring Si), and has a perforated arm 5t extending upward and carrying a curved abutment face 56 substantially plunger 56. A tab 5B punched and bent down out of the longitudinal strip portion kM of the rider 40 engages the abutment face 56 of the belll crank arm 56, for driving the bell crank toward the right, as seen in the drawing, with the forward motion of the plunger 28.

A forward extending arm 80 of the bell crank lies above the operating pin 22 of the unitary switch I8 for depressing it and operating the switch in response to the forward driving motion of the actuating plunger 28. A coil spring 82 connected between the bracket 30 and the upper end of the bell crank arm 54, serves to retract the bell crank and with it the rider 40 and plunger `28 to their normal position as shown in Fig. 1.

When the actuating plunger 28 is moved forward (toward the right) as shown in Fig. 3, the resulting forward motion of the rider 40 drives the bell crank U against the operating pin 22 of the switch I8 for operating it, and the resilience of the spring 48 permits the plunger 2B to continue its forward motion beyond the point at which the switch I8 operates. The considerable "overtravel" motion of the plunger 26 can be noted in Fig. 3 where the plunger 28, moved to its extreme forward position has carried the key 48 away from the end 42 of the rider 4I?.

The large diameter portion of the plunger 28 is hollow, and threaded to receive a headed extension screw Bt which may be adjusted to vary the effective length of the plunger. The housing may be mounted either by a pair of integral mounting lugs B8, or by screws threaded into the holes I6.

The lower surface of the arm 60 of the bell crank 60 is parallel to the axis of the bell crank pivot 52, which in turn is parallel to the two supporting pins 20 of the unitary switch IB. Accordingly, movement of the switch I8 on its two pins will not, by itself, bring the actuating pin 22 into engagement with a higher or lower spot of the bell crank arm 80. That is, movement of unitary switch I8 on its pins 22 cannot effect operation of switch I8 by the plunger 26 and bell crank 50.

'Ihroughout the specification and claims, directional terms such as above, below, horizontal, vertical, forward, etc. are used for convenience and for indicating relative directions and are not used in a restrictive sense.

It will be apparent to those skilled in the art that the present invention is capable of numerous modifications and variations, and that the particular embodiment herein shown and described serves simply as an example. Accordingly the invention is to be limited only in `accordance with the scope of the appended claims.

I claim:

l. In combination in a construction of the class described; a reciprocable actuating plunger, a rider carried by said plunger and slideable lengthwise thereon, a spring holding said rider forward on said plunger, a stop on said plunger for limiting the forward motion of the rider thereon, a bell crank supported separately from said plunger and rider, and abutting said rider to be driven by the forward motion of said rider, and a spring for urging said bell crank against said rider.

2. In combination in a construction of the class described, a reciprocable actuating plunger, a rider carried by said plunger and slideable lengthwise thereon, a spring holding said rider forward on said plunger, a stop on said plunger for limiting the forward motion of the rider thereon, and a bell crank supported separately from said plunger and rider, said bell crank having an arm abutting said rider so as to be driven by the forward motion thereof, and having another arm for transmitting the driving force of said rider in a direction at an angle to the forward motion of said plunger.

3. In combination in a compact actuator construction of the class described, a reciprocable actuating plunger, a rider carried by said plunger and slideable lengthwise thereon, a spring urging said rider forward on said plunger, a stop on said plunger for limiting the forward motion of said rider thereon, a bell crank having a pivot axis close to the plunger at one side thereof, the bell crank having an arm extending across said plunger, and having an abutment face on said arm for engagement by said rider at a position across said plunger from the bell crank pivot, whereby the effective lever arm length is longer than the spacing between the plunger and the pivot axis.

4. In combination in a compact actuator construction of the class described, a reciprocable actuating plunger, a rider carried by said plunger and slideable lengthwise thereon, said rider constituting 9. strip lying above said plunger and having down-turned, perforated ends slideably fitting said plunger, a spring encircling said plunger between the down-turned ends of said rider and bearing against the forward end of said rider to urge it forward on said plunger, a stop for abutting the rearward down-turned end of said rider for limiting the forward motion of said rider on said plunger, a bell crank having its pivot axis below said plunger, and having an arm extending to a point above said plunger to provide an abutment surface above said plunger, said rider having an abutment extending down from said strip so as to lie between said strip and said plunger for engaging said abutment surface of said arm so that the forward motion of said plunger and rider drives said bell crank.

5. In combination in a compact actuator con struction of the class described, a bearing for a reciprocable plunger, a plunger in said bearing, said plunger having an unsupported end extending forward beyond said bearing, a rider carried by said extended end of said plunger and slideable thereon, said rider consitituting a strip lying above said plunger and having downturned perforated ends slideably fitting said plunger, said plunger having a large diameter to flt said bearing and a smaller diameter portion constituting most of said extended end thereof, one end of said rider fitting the large diameter and the other fitting the small diameter of said plunger, a spring bearing at one end against the shoulder between said large and small diameters of said plunger and at the other end against the forward end of said rider, a stop near said shoulder for abutting the rearward end of said rider for limiting the forward motion of said rider on said plunger, a bell crank pivoted on a shaft lying below said plunger and perpendicular thereto, said bell crank having an arm extending upward alongside said plunger and having an abutment face on said arm in a position above said plunger and between said plunger and strip, said rider having an abutment extending downward from said strip and engaging said abutment surface of said arm for driving said bell crank forward'with said plunger and rider, and a spring for rotating said bell crank against said abutment of said rider.

MALCOLM W. EATON. 

